Nel Backstory "Spoilers", in other words, the preliminary events that went on that he doesn't know about:
Nel's family had a history of magical practice. The high vampire courts of Europe, or at least one sect of them, targeted him and actively made life worse on him so that when he died his spirit would be vengeful and malicious. Magic users are more susceptible to becoming vampires or other undead when they die, so they knew if he was furious enough, he would come back as a nelapsi, a vampire renowned for its bloodthirst and power. They're exceedingly rare, and the Courts saw their opportunity to cultivate one to join their ranks.
When Nel rose from the dead, he was just a horrible as they planned, and levelled and fed on his entire village in the night. An ambassador of the Court was positioned in the village to 'bring in' the nelapsi once his blood rage wore out, but Nel retreated into the wilderness and inadvertently threw the Court ambassador for a loop. Nel's remorse set in shortly after the frenzy, and so the Court never found their chance to seize him at another mass feeding. Nel never really knew anybody was out to find him. Except, now that Nel is older, he has this almost sixth-sense (or he brushes it off as paranoia) when there's something...wrong near. Some nights alone at his estate are absolutely nerve-wracking. He does fear for himself and his loved ones, but because he doesn't know what is threatening him, he never lets onto it.
The Court has been trying to locate him for years, and in hearing what he's become, they're utterly ashamed and furious that their 'terrible vampire' is cavorting with humans and has little magical prowess.
